A search for athletes named Dee turns up a short list: There's Dee Virgil Fondy, who played major league baseball from 1951 to 1958, and was the last player to bat at Brooklyn’s Ebbets Field; Dee Hardison, a defensive lineman for the Buffalo Bills, New York Giants, San Diego Chargers, and Kansas City Chiefs in the 1970s and 1980s; and DeCovan “Dee” Brown, who spent 12 seasons in the NBA and won the league's Slam Dunk Contest in 1991.

Their strengths were moxie and muscle. That’s something another D — vitamin D — definitely contributes.

A study out of Trinity College Dublin reveals that just as regular exercise is essential for maintaining muscle mass and function as you age, so is sufficient vitamin D.

The researchers tested blood levels of vitamin D in 4,157 people 60 and older, and then assessed their grip strength and tested their balance, agility, gait speed, and ability to rise from a chair without using their hands.

Those with the lowest blood levels of vitamin D — below 30 nmol/L, the level signaling deficiency and onset of bone disease — had twice the muscle weakness and three times the difficulty with muscle performance as people with a level of 50 nmol/L or more.

For major-league performance as you age, get an annual blood test to determine what supplementation you need to achieve a level of 50-80 nmol/L.

Until then, if you're over 50 take 2,000 IU of D2 or D3 daily. You can also get vitamin D from foods such as salmon, most cultivated mushrooms, and D-fortified cereals and soy milk.